I. Field of the Invention
The present invention refers to the cutting of hollow articles made of glass, plastic and the like and, more specifically, to a process and machine for simultaneously cutting off the excess ends of hollow, semi-finished glass articles, such as the tubes enlarged at their mid portion, for the so-called "oil lamps", said invention being adapted for inclusion as part of the article forming process and machines for the continuous production of such articles.
The process comprises, in combination, the stages of: retaining and/or holding the semi-finished article vertically, horizontally or rotationally by the portion of the article intermediate its ends; rotationally holding at least one of excess ends of the semi-finished article, in synchronism with the rotational retention and/or holding of the middle portion thereof; simultaneously beginning the thermal, electromagnetic or mechanical cutting off of both excess ends of the article; lightly pulling at a predetermined rate and in synchronism with the cuts, at least one of the rotationally-retained ends, and when both cuts are finished, free the retained surplus pieces, to fall by gravity to a surplus collector, before or after the finished article has been withdrawn.
The machine comprises, in combination: a rotary support and/or holding base hereinafter named impeller, suitable for placing and/or holding vertically or horizontally or rotationally a semi-finished article by the portion intermediate its ends; two cutters, either thermal, electromagnetic or mechanical, located at the height of the excess portions it is desired to cut off and, if desired, rounding the cut ends of the article; a surplus collector wherein the surplus portions fall and are collected; at least one rotary holder that turns in synchronism with the impeller and which holds and slightly pulls, at a predetermined speed and in sychronism with the cutting operation, at least one of the excess ends of the article in such a manner that, when both cutters finish the cutting operation and, if desired, the rounding or edging work, release the surplus portions to fall by gravity to the collector.
II. Description of the Prior Art
Currently, only the processes for thermal cutting of glass articles are known, in which the two thermal cuts are made separately, in different machines and with the article in a vertical position.
The first step consists of an operator placing the semi-finished article in the first cutting machine, with the article held by its enlarged, middle part or by its closed end on a rotating holding base, hereinafter, called an impeller, which employs a vacuum to perform its function, the lower excess part or open end of the article being downwardly positioned; the impeller is rotated by a transmission and has been preheated in order not to shatter the article; thereafter, a two-part burner is placed in proximity with or surrounds the excess lower part, said burner having a series of slots and/or apertures located about the perimeter of its inside diameter. A flame produced by the combustion of combustible gas and oxygen is forced through each slot. The burner also has adjustable guides for centering the article; said guides being of a suitable material, which will not shatter, crack or mark the glass product.
The burner heats an imaginary lower-cut line to bring the glass, plastic or like material to a definite temperature and at this moment the weight of the excess breaks the glass surface tension and such excess or surplus falls by gravity, thus completing the first cut. Thereafter, the burner is left in operation for a short lapse of time to smooth the cut end of the article and provide the final finish thereof. Next, the two-part burner is opened and withdrawn, leaving sufficient space to withdraw the article, the vacuum for retaining the article in the holder being cut off. Another operator transports the article to the second cutting machine, placing it on the impeller or rotating holding base. The article, this time, is located with the previously cut end facing upwardly, the excess upper part or closed end to be cut being directed downwardly.
At this stage a pneumatic cylinder located at the top of the machine lowers a tapering or centering device, which penetrates the end of the freshly cut article for centering same.
A two-part burner which also is provided with slots or apertures located about the inner periphery thereof for producing flames, resulting from the combustion of combustible gas and oxygen is moved to or locked in proximity to the depending upper excess part of the article. The burner heats the imaginary cutting line to bring it to a definite temperature and at this time the weight of the surplus breaks the glass surface tension, thus effecting the second cut. Next, the flame from the burner edges or rounds the cut article for a brief time, in order to attain a final smooth finish. The two-part burner is then opened and withdrawn and at the same time, the upper pneumatic cylinder removes the centering device, leaving sufficient space to remove the finished article.
These conventional cutting processes, which are known in the art, have the considerable disadvantage in that the two cuts must be performed with the article in a vertical position only, and also requires two machines, one for the first cut and one for the second cut.
Consequently, these conventional processes require a sizable investment in machinery, a considerable amount of labor and a series of expenses that increase the price of the finished product.
Furthermore even if it were possible to make both cuts by use of only one machine, as could be feasible if both excess ends would be at the same distance from the retained central part of the article, and also if certain modifications were made in the machine, it would still be necessary to make the cut in two stages, one for cutting the excess lower part and the other to cut the excess upper part, since it is necessary to make both cuts with the article vertically located and there would be no way to cut, pull and hold the cut off end for separation from the article and subsequent rejection.
On the other hand, no thought had been given to the idea that the cuts could be performed other than by the thermal cutting as is now possible with the present invention, because of use of a combination of holders for the excess parts, it is now possible to make the cuts both mechanically (e.g. with chisels or gravers) and electro-magentically (e.g. with laser beam) as well as by thermal cutting and with the article either in vertical or horizontal position.